<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
      function Person(){
          this.name = "yyf"
      }
      Person.age=18
      var a = new Person()
      arr1 = [1,2,3,4]
      arr2 = [2,3,4]
      function div(arr1,arr2){
         arr3 =  arr2.filter(v=>{return arr1.includes(v) })
         arr4 =  arr2.filter(v=>{return !arr3.includes(v)})
         return arr4
      }
      var arr3 = div(arr1,arr2)

      var name = "yyf"
      function ass(){
        console.log(name)
        name = 123
        console.log(window.name)
        var name = "欢迎您"
        console.log(name)
      }
      ass()
    </script>
</body>
</html>